Override handler for allocation id – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 2.7-2.9

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Briefly, this error occurs when OpenSearch tries to allocate a shard to a node but finds an existing shard with the same allocation ID. This could be due to a misconfiguration or a network partition. To resolve this issue, you can try the following: 1) Check the cluster health and ensure all nodes are connected. 2) Verify the shard allocation settings in your OpenSearch configuration. 3) If the error persists, you may need to manually remove the conflicting shard and allow OpenSearch to reallocate it. Always ensure you have a backup before performing any manual operations.

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This guide will help you check for common problems that cause the log ” Override handler for allocation id {} ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: handler, replication, indices, allocation.

Log Context

Log “Override handler for allocation id {}” classname is OngoingSegmentReplications.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

    CopyState prepareForReplication(CheckpointInfoRequest request; FileChunkWriter fileChunkWriter) throws IOException {
        final CopyState copyState = getCachedCopyState(request.getCheckpoint());
        allocationIdToHandlers.compute(request.getTargetAllocationId(); (allocationId; segrepHandler) -> {
            if (segrepHandler != null) {
                logger.warn("Override handler for allocation id {}"; request.getTargetAllocationId());
                cancelHandlers(handler -> handler.getAllocationId().equals(request.getTargetAllocationId()); "cancel due to retry");
            return createTargetHandler(request.getTargetNode(); copyState; request.getTargetAllocationId(); fileChunkWriter);
        return copyState;


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